Quantification of relative afferent pupillary defects induced by posteriorsub-Tenon's, peribulbar, and retrobulbar anaesthetics

Aims-The effect of local anaesthetics on optic nerve function can be invest igated by quantifying the relative afferent pupillary defect (RAPD). Methods-The study compared the depth of induced RAPD following posterior su b-Tenon's, retrobulbar, and peribulbar local anaesthetics using crossed pol arising filters before cataract surgery (time 1 = 5 minutes), immediately a fter surgery (time 2 = 42 minutes (av)), and once again on the ward (time 3 = 107 minutes (av)). Results-All patients developed a RAPD. There was no significant difference in the depth of RAPD between the groups at any one time period. The peribul bar group had a significantly steeper decay in RAPD from time 1 to time 2 ( p = 0.014). This effect was reduced when the shorter operation time for thi s group was entered as a cofactor (p = 0.063). By time 3 the RAPDs for all groups had decayed similarly so that no differences could be detected. Conclusion-All three anaesthetic methods caused a similar level of disrupti on to optic nerve conduction immediately following administration and at th e time of day case discharge.